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Date: Fri, 6 Sep 2013 10:00:44 -0700
From: Christoph Hellwig <hch@infradead.org>
To: "J. Bruce Fields" <bfields@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>, linux-nfs@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, Nick Piggin <npiggin@kernel.dk>
Subject: Re: [PATCH 1/3] dcache: use IS_ROOT to decide where dentry is hashed
Message-ID: <20130906170044.GA6460@infradead.org>
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On Fri, Sep 06, 2013 at 11:43:48AM -0400, J. Bruce Fields wrote:
> diff --git a/fs/dcache.c b/fs/dcache.c
> index b949af8..934f02d 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -393,7 +393,7 @@ static void __d_shrink(struct dentry *dentry)
>  {
>  	if (!d_unhashed(dentry)) {
>  		struct hlist_bl_head *b;
> -		if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
> +		if (unlikely(IS_ROOT(dentry)))

I think this needs a comment about why the IS_ROOT check is fine,
destilled from your commit log.

Also while reviewing this I noticed that one of the two callers of
__d_shrink already has the d_unhashed check - it might make sense to
move it to the other caller as well if you touch this area anyway.
(as a separate patch).